Genomic surgery has also become available to adults
New DNA Editing Method eliminates genetic diseases
Kirill Stasevich, CompulentaThe increasingly popular method of molecular genetic editing CRISPR is based on a virus protection system used by bacteria and archaea.
One of the key components of the latter is the Cas9 protein, which, with the help of service RNAs, can cut a specific piece from DNA (in bacteria and archaea, it attacks viral DNA without touching the DNA of the cell). By modifying this enzyme and the RNA that lead it to the place of work, you can edit the right gene with high accuracy: Cas9 will come exactly where you need it and cut out exactly what you need.
Not so long ago, we reported on a kind of achievement of Chinese scientists who managed to get monkeys with an edited genome. Editing was carried out using the CRISPR/Cas9 system, and the experiment itself was set with embryos. Although the effectiveness of the method turned out to be low, scientists managed to prove the fundamental feasibility of such manipulations.
However, when mentioning such operations with DNA, genetic diseases come to mind first of all: in the future, with the help of genetic engineering methods, we must learn to purposefully get rid of bad mutations in our DNA and do it not at the embryo stage, but already in an adult organism. It was such an operation that researchers from the Massachusetts Institute of Technology (USA) succeeded. However, not on humans and not even on monkeys, but on mice.
Daniel G. Anderson and his colleagues worked with animals suffering from tyrosinemia. This disease is caused by a mutation in the gene of the enzyme fumarylacetoacetate hydroxylase (FAH): due to the mutation, the amino acid tyrosine ceases to be cleaved, and the resulting metabolic problems lead to damage to the liver, as well as kidneys and nerves. In humans, tyrosinemia occurs with a probability of 1 in 100,000, and its symptoms can be mitigated only by reducing the content of tyrosine in the body.
The mice were completely cured of the disease. Animals were injected with specially designed RNA molecules that sent the Cas9 enzyme to the desired gene, as well as a 199-nucleotide DNA segment with a "healthy" sequence of the FAH gene. According to the authors of the work in Nature Biotechnology (Hao Yin et al., Genome editing with Cas9 in adult mice corrects a disease mutation and phenotype), the replacement was successful in less than half a percent of all hepatocytes, but thanks to the division of the latter in a month, a third of liver cells were replaced with healthy ones in which there was no mutation in FAH.
This turned out to be enough to leave the mice without the usual supportive medications: the animals did not die, although no one artificially lowered their tyrosine levels.
It is clear that this method is far from perfect, that if we talk about clinical trials, then we need to think about more effective and convenient ways of delivering genetic and chirurgical molecules into the body. However, in this case, it is important that the technology works in the adult body, and not in the embryo, and in the future it will be possible to treat a variety of diseases, from hemophilia to Huntington's syndrome.
Prepared based on the materials of MIT News: Erasing a genetic mutation.
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